How do I copy vertex groups from one object to another?
Vertex groups are object data, so they will be copied by &#9096; CtrlL> Object data.
However, this will link all other object data as well.

For a onetime copy of only object data, you might want to try the bundled Copy attributes addon.

Once it's enabled, call it with &#9096; CtrlC (warning, this conflicts with object copy/paste):